Stencil sheet



Faitente do 16, I931 OFFICE- CRLES I. KUMLI, OF CHICAGO, ILLINOIS, ASSIGNOR, BY MESNE ASSIGNMENTS, TO SELECTOGRAPH COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS STENCIL SHEET No Drawing.

This invention relates to stencils and particularly to stencil sheets comprising a fibrous, porous support, such a Japanese yoshino paper, having a hardened coating of organic colloid, impervious to ink, in which the stencil characters are cut, by the expression process, to permit the ink or other coloring to print through the fibers of the paper or other porous support.

One of the common types of stencils long in use consisted of yoshino paper coated with gelatin which was coagulated either by an aluminum salt, or by a chrome salt such as potassium dichromate, which chemically combined with the gelatin to form a hard coating.

In order to adapt the coated sheet for making the stencil by pressure, as for instance by the impact of the types of a typewriter,

the sheet must be dampened so as to permit the type to rupture the impervious film without cutting or otherwise injuring the fiber of the paper. In dampening coated sheets which have been hardened by aluminum salts alone. the fibers of the paper have a tendency to stretch so as to cause the stencil to become baggy in its frame, and the paper has a tendency to become sticky. For this reason, aluminum salts have not been satisfactory as hardening agents.

When potassium dichromate is used alone as the hardening agent. the sheet must be exposed to light. because the coagulating action of potamiu m dichromate on the organic colloid is dependent upon a light reaction. In order to expose the sheets so that their entire surfaces are acted upon by the light. a large amount of floor space is required if the stencils are to be manufactured in considerable quantities. The use of potassium dichromate alone is, therefore, objectionable.

The main objects of this invention are to provide an improved coating material which is waterproof and which has none of the aforementioned objectionable characteristics inherent in solutions containing chrome or aluminum salts; to' provide a stencil sheet which is tough and waterproof and which will not become baggy when dampened; and

Application filed December 20, 1928. Serial No. 327,481.

to provide an improved method of preparing a stencil sheet.

Stencils may be made of any suitable fibrous, porous material, but Japanese yoshino paper is preferred because of its thin texture.

In carrying out this invention, the sheet is coated preferably in two successive steps. In the first step the sheet is coated with a solution which preferably includes glue,

glycerine and a volative vehicle and then, after the paper is dried, the sheet is coated with a water soluble permanganate.

The glue is the principal ingredient and gives the sheet the desired ink-resisting surface. Any suitable organic colloid, such as gelatin, agar-agar, or Irish moss may be used. A good grade of hide glue has been found to be very satisfactory.

The glycerine is the tempering agent. The sheet, after being coated, is kept in a flexible condition by the glycerine which retains enough moisture to keep the sheet from becoming brittle. The glycerine may be re placed by any other suitable tempering agent such as glucose, sugar, or mon acetin.

The volatile vehicle may be water or any other suitable solvent which evaporates quickly after the film has been applied to the sheet.

The ingredients of the aforementioned solution may be combined in various proportions, but it has been found that satisfactory results can be obtained from a combination in the following proportions:

Parts bv I weight Glue 22 Glycerine 40 Water 210 In order to dissolve the glue, it is soaked in cold water from 4 to 10 hours. The glycerine is then added and the mixture heated to about 70 C.

After the mixture of glue, water and glycerine has been heated, it is cooled to about 35 C. and maintained at this temperature while it is applied to the sheet.

The sheet may be impregnated with the coating solution by any of the well known methods. 2

After the first coating has been applied, the sheet is driedand then coated with a 2% solution of potassium permanganate, which coagulates the glue and renders the sheet waterproof.

Although this invention is here particularly described in its preferred embodiment, it will be understood that the product and the various steps of the process may be modified by omission or alteration of details and substitution of ingredients, without departing from the s irit of the invention as defined by the following claims.

I claim:

1. A stencil sheet comprising a porous base coated with a mixture of an organiccolloid, a tempering agent and a water soluble permanganate.

2. A stencil sheet comprising a porous base coated with a mixture of a protein colloid, a tempering agent, and a water soluble permanganate.

3. A stencil sheet comprising a porous base coated with a mixture of glue, a tempering agent, and a water soluble permanganate.

4. A stencil sheet comprising a porous base coated with a mixture of an or anic colloid, a tempering agent, and potassium permanganate. Y

5. A stencil sheet comprising a porous base coated with a. mixture of a protein colloid, a tempering agent, and potassium permanate.

6. A stencil sheet comprising a porous base coated with a mixture of glue, a tempering agent, and potassium permanganate.

7. A composition for use in coati the porous base of a stencil sheet compris a mixture of glue, a tempering agent, an a dilute solution of a water soluble permanganate.

8. A composition for use. in coating the porous base of a stencil sheet comprising a mixture of 22 parts of an organic colloid, about 210 parts of water, 40 parts of a tempering agent, and a water soluble permanganate.

9. A composition for use in coat the porous base of a stencil sheet comprismg a mixture of about 22 parts of glue, about 210 parts of water, 40 parts of a tempering agent, and potassium permanganate.

10. The process of coating a porous stencil sheet comprising mixing an organic colldid with a tem erin agent in aqueous solution, applyin drying t e so-treated sheet, and coagulating the colloid with a water soluble permanganate.

tempering agent 1n aqueous solution, applying the mixture to the stencil sheet, drying t e mixture to the stencil sheet,

a porous sheet the so-treated sheet, and coagulating the colloid with potassium permanganate.

12. The process of coating a porous stencil sheet comprising mixing a protein colloid with a temperin agent in aqueous solution, applying the mlxture to the stencil sheet, drying the so-treated sheet, and coa lating the protein colloid with a water solu le permanganate.

13. The process of coating a porous stencil sheet comprising mixin a protein colloid with a tempering agent in aqueous solution, applying the mixture to the stencil sheet, drying the so-treated sheet, and coagulating the protein colloid with potassium permanganate.

14. The process of coating a porous stencil sheet comprising mixing a protein colloid with a tempering agent in aqueous solution, applying the mixtureto the stencil sheet, drying the so-treated sheet, and coagulating the protein colloid with a dilute solution of potassium permanganate.

Signed at Chicago this 17th day of December, 1928.

CHARLES F. KUMLI. 

